Study on energy flows of renewable sources for producing hot water on dairy farms

R. Georgiev1, K. Peychev1, D. Georgiev1, R. Slavov2*, S. Apostolov3, J. Ellingsen4, J. Tønnesen4

1Depertment of Agricultural Engineering, Faculty of Agriculture,Trakia University, 6000 Stara Zagora, Bulgaria
2Department of Animal Science – Ruminants and Dairy Farming, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria 3Bioselena Foundation for Organic Agriculture, Bulgaria
4Royal Norwegian Society for Development, Norges Vel, Norway

(Manuscript received 10 May 2016; accepted for publication 2 August 2016)

Abstract. A system for producing hot water in three dairy farms has been designed and built. It consists of three modules of renewable energy sources – solar thermal installation, heating boiler on wood pellets and recuperative unit for utilizing heat from the milked milk. For storage of the heated water two thermal batteries are used. One of the thermal batteries is a low temperature one (40°С) and is designed to utilize energy from milk, the other one is high-temperature (80°С) and is designed to accumulate solar energy and energy from the pellet boiler. The year-round operation of the system on three different farms has been examined. For every month results were obtained about the relative share of each of the renewable energies. Each system produces annually respectively 11273 kWh, 13668 kWh and 10244 kWh of energy to heat water. The share of solar energy is between 34.7 – 43.0% in annual terms, in summer it reaches 85- 95%. The share of energy from pellets per year is 52 – 57%, in winter it reaches 65 – 96%, while the share of utilized energy from milked milk averaged 9.5% annually.